dreamlandjs/html.js

export function html(strings, ...values) {
  let flattened = "";
  let markers = {};
  for (const i in strings) {
    let string = strings[i];
    let value = values[i];

    flattened += string;
    if (i < values.length) {
      let dupe = Object.values(markers).findIndex(v => v == value);
      if (dupe !== -1) {
        flattened += Object.keys(markers)[dupe];
      } else {
        let marker = "m" + Array(16).fill(0).map(() => Math.floor(Math.random() * 16).toString(16)).join("");
        markers[marker] = value;
        flattened += marker;
      }
    }
  }
  let dom = new DOMParser().parseFromString(flattened, "text/html");
  if (dom.body.children.length !== 1)
    throw "html builder needs exactly one child";

  function wraph(elm) {
    let nodename = elm.nodeName.toLowerCase();
    if (nodename === "#text")
      return elm.textContent;
    if (nodename in markers)
      nodename = markers[nodename];

    let children = [...elm.childNodes].map(wraph);
    for (let i = 0; i < children.length; i++) {
      let text = children[i];
      if (typeof text !== "string") continue;
      for (const [marker, value] of Object.entries(markers)) {
        if (!text) break;
        if (!text.includes(marker)) continue;
        let before;
        [before, text] = text.split(marker);
        children = [
          ...children.slice(0, i),
          before,
          value,
          text,
          ...children.slice(i + 1)
        ];
        i += 2;
      }
    }

    let attributes = {};
    for (const attr of [...elm.attributes]) {
      let val = attr.nodeValue;
      if (val in markers)
        val = markers[val];
      attributes[attr.name] = val;
    }

    return h(nodename, attributes, children);
  }

  return wraph(dom.body.children[0]);
}